Expert: Dan Liddy - 4/21/2004

Question
 I have a question in regaurds to engine cooling and building.  I have researched that a lower thermostat will help keep your engine cooler.  I have a 2001 Nissan Sentra SE 2.OL (SR20DE low port engine with roller rocker cam) with a NISMO thermostat that kicks on at 150f.  The stock one was around 167f.  The problem is it kicks on the "service engine light."  Is it even worth the difference for the performance of the engine and will it increase the longevity of the car?  I talked to one Nissan engine builder who said to stick with the stock thermostat as it is actually better for performance.  The only way to get rid of the light is to switch back to stock.  What should I do?  

 Also is it worth the effort to install an oil cooler to a vehicle to aid with oil cooling?  Does it help with performance and if so how?

 I also have a question concerning fuel presure regulators.  For an all NA car I have been told that they are not needed, however I have been told they can increase horsepower.  My current stock injectors work fine.  Will the addition of the regulator and bumping up the pressure give me more horsepower.  The model I am interested in adjusts from 28.4-85.2psi.  What's the max pressue I could bump to and would putting higher flowing injectors help or assist if I add the fuel pressure regulator?

 Thanks helping and I hope my qestions were in your lane!

 Very Respectfully,
          Justin Miller

Answer
Hi Justin:

Question #1 about the thermostat, your friend is correct, the engine will perform best at around 190 F  so stay with the stock thermostat, or get one for northern climates.

Question #2 Oil coolers are usually for racing but will benefit a street car as well. Petroleum oils break down badly at anything over 250 deg. f , and most engines run at those temps or higher.  The other thing you should DEFINATELY do is switch to a synthetic oil. I recommend Castrol Syntec, and for my racing I use Amzoil exclusively. I do NOT recommend Mobil One, It's cost me at least one engine, and doesn't hold up in a hot engine.

Question #3 most FI engines need about 36 Lb. of fuel pressure, first I would suggest you get a fuel pressure guage from Summit Racing (www.summitracing.com) and install that, then decide whether you need more pressure or not. Most Nissans come with a good system already. As to switching injectors, it's a matter of experimenting , lean engines run stronger than those that are running rich. Your spark plugs should have a milk chocolate brown residue on the insulators, down deep within the plug.  You should run maybe 10-15 miles on the Interstate as fast as you dare, then shut off the engine AT SPEED, coast to a stop, and remove and inspect the plugs. If they are white, it's too lean, if they are dark brown or black it's too rich. Usually changing injectors up one size adds a little punch to it, but it's an expensive experiment. They aren't cheap, and they aren't returnable if you buy the wrong size.

Hope the above has been a help, good luck with your projects.

Dan Liddy
Sarasota, Florida